Twelve diel surveys were carried out in three reservoirs of Sri Lanka viz. Minneriya, Udawalawe and Victoria, to investigate diel feeding patterns, daily ration and relative food consumption in fish populations. Stomach content weights of different size classes of various fish species in the three reservoirs in 12 diel surveys were analysed using an iterative method, MAXIMS. Predominantly herbivorous or detritivorous fish species such as Amblypharyngodon melettinus and Oreochromis niloticus exhibited one peak in the diel feeding pattern. Two peak feeding periods were evident in predominantly insectivores and/or zooplanktivores (e.g., Puntius chola and Rasbora daniconius) and interestingly in macrophyte feeders (i.e., Etroplus suratensis, Puntius filamentosus and Tilapia rendalli). It might be possible that all species with two feeding peaks in diel feeding patterns rely on vision for feeding. Food consumption per biomass (Q/B ratio) defined as amount of food consumed per unit weight of an age-structured population of fish was estimated on the basis of the average quantities of food consumed over a long period of time by various size classes in order to minimize the bias of estimates.Résumé -Périodicité nycthémérale d'alimentation, ration journalière et consommation relative chez des poissons de trois lacs artificiels du Sri Lanka. Douze séries d'échantillonnage ont été effectuées dans trois lacs-réservoirs du Sri Lanka : Minneriya, Udawalawe et Victoria, afin d'étudier le modèle journalier d'alimentation, les rations journalières et à la consommation relative des populations de poissons. Les poids des contenus stomacaux de différentes classes de taille ont ainsi été analysés en utilisant une méthode itérative, MAXIMS. Les espèces herbivores ou détritivores telles que Amblypharyngodon melettinus et Oreochromis niloticus montrent un pic dans l'activité de nutrition. Tandis que les espèces détrivores et/ou zooplanctivores en présentent deux (ex., Puntius chola et Rasbora daniconius) de même que des espèces se nourrissant de macrophytes (ex., Etroplus suratensis, Puntius filamentosus et Tilapia rendalli). Il est possible que la vision joue un rôle chez ces espèces présentant deux pics journaliers d'alimentation. La consommation de nourriture par rapport à la biomasse (le rapport Q/B) est défini comme la quantité d'aliment consommé par unité de poids d'une population de poissons structurée en âge, sur la base de quantités moyennes de nourriture consommée sur une longue période de temps et par diverses classes de taille, afin de minimiser les biais dans les estimations.

Caves and karst-like features in Proterozoic gneiss and Cambrian granite, southern and central Sri Lanka: An introduction. There has been little study of the geology and geomorphology of the caves and karstlike features developed in the Proterozo ic gneiss and Cambrian granite of Sri Lanka. This lack of study is surprising given that caves and rockshelters in these rocks contain significant archaeological and cultural sites. Caves and karren, both mimicking those developed in carbonate rocks, have formed both in gneiss, which is the dominant rock type of the Proterozoic crust of the island and in granite. In addition to overhangs, boulder caves, soil pipes and tectonic caves, tunnel caves, arch caves and block breakdown caves of significant size are developed in siliceous rocks in Sri Lanka. while metamor phosed dolomites are interfoliated within the gneissic suite, simple removal of carbonate by solution from within the sur rounding rock cannot account for all or most of the speleogen esis observed. while spalling and breakdown are responsible for cave enlargement, cave initiation is probably due to either phreatic solution of silicates and/or phantom rock processes. Speleothems and cave minerals including silicates, phosphates, gypsum, carbonates and niter are found in the caves. Active silicate speleothems are not restricted to joints and fissures and suggest that solution of silicates is currently occurring within the body of the rock in the vadose zone. while guano is the likely source of the phosphate, sulfate and nitrate, the source of the calcium in the carbonates remains unclear. Caves in the intrusive and metamorphic rocks of Sri Lanka are enigmatic. They are unexpectedly similar in appearance to their carbon ate karst counterparts. Continuing research will allow them to hold a mirror to our understanding of speleogenesis, mineral ization and sedimentation in carbonate karst caves.

Discharge-mediated seasonal patterns of food web interactions were investigated in two streams in Sri Lanka; Eswathu Oya (a perennial wet-zone stream) and Yan Oya (a seasonal dryzone stream). Based on volumetric proportions of diet composition, relative abundance of fish species and their daily food rations, the mean cumulative consumption of each prey taxon was estimated for each fish population. Food web diagrams were prepared using trophic index of fish, trophic class of prey and feeding interactions between fish and prey. Both streams showed seasonal patterns of discharge due to rainfall, but no significant effect was evident in the trophic index of most fish species. In both streams, cumulative consumption of prey taxa was highest during low discharge regime due to increased abundance of both prey taxa and consumers. In Eswathu Oya, diversity of prey taxa was higher during the low discharge regime, but in Yan Oya, high diversity occurred during the high discharge regime. Herbivorous and/or detritivorous fish species were rare in Eswathu Oya but dominant in Yan Oya. Complex food web structure in Yan Oya due to high fish species richness and high diversity of prey categories made it less sensitive to discharge extremes in contrast to relatively simple food web structure in Eswathu Oya. This study, therefore, highlights the importance of maintaining the quality of riparian environments for conservation of biodiversity. K E Y W O R D S feeding ecology, fish fauna, flow regime, trophic index, tropical streams Internat Rev Hydrobiol. 2017;102:3-14.wileyonlinelibrary.com/journal/iroh

The benthic macroinvertebrate fauna and main abiotic parameters were studied to understand the patterns of diversity and structure along the temporal and longitudinal gradients in two tropical lotic ecosystems in the wet and dry zones of Sri Lanka. Invertebrate abundance (annual means) was in the same magnitude in the two streams (2,520 ind. m−2 in the wet zone stream and 2,940 ind. m−2 in the dry zone stream). Both streams had similar annual mean diversity levels measured as Shannon diversity (Eswathu Oya (wet zone) = 2.11; Yan Oya (dry zone) = 2.07), with a mean annual evenness (Pielou evenness) of 0.56 ± 0.14 for Eswathu Oya and 0.60 ± 0.09 for Yan Oya. Along the longitudinal gradient, abundance and taxa richness increased toward the lower reaches in the wet zone stream but decreased in the dry zone stream. Composition of functional feeding groups was greatly influenced by abiotic factors in the temporal gradient than in the longitudinal gradient. This was possibly due to the seasonal patterns of flow regimes, and allochthonous nutrient inputs into the streams. Hence, resource management and conservation as well as attempts of ecological assessment in tropical streams should be based not only on the in‐stream characteristics but also on the catchment properties.

In the present paper, an attempt is made to investigate whether the body shape indices can be used to predict food habits of fish species in three reservoir fish communities of Sri Lanka. The present analysis is based on the studies on food and feeding habits of fish species and their body shape indices in three Sri Lankan reservoirs, namely Minneriya, Udawalawe and Victoria. Body proportions of individual fish species were determined as P1 (= Maximum height of the body/ Maximum width of the body) and P2 (= Total length/ Maximum height of the body), which were found to be negative curvilinearly related. Trophic indices (Ti) of individual fish species were determined on the basis of trophic level of each food item and the fractions of all food items consumed by fish species, which ranged from 1 for exclusively herbivorous species to 3 for carnivorous species. A negative logarithmic relationship between P1 and Ti indicates that laterally compressed fish species with deep bodies feed on lower trophic levels in the food web. On the other hand, dorso-ventrally flattened species with low P1 have higher trophic indices than those with high P1. The positive logarithmic relationship between P2 and Ti also indicates that short, deep-bodied fish species representing low P2 values feed on lower trophic levels whereas slender, long-bodied species with high P2 values feed on higher trophic levels. The body shapes, measured as simple body proportions of the definitions of P1 and P2, can therefore be used to predict feeding habits of fish.